Enter John Thune.

By way of Mike Allen's Playbook is Stephen Hayes' Weekly Standardpiece on South Dakota Sen. John Thune. According to Hayes, Thune -- touted previously by David Brooks -- has all but committed to a run for the Republican presidential nomination in 2012:

Several people close to the senator say they would be surprised if he chose not to run, and Thune allows that he’s thinking about it seriously enough that he’s gamed out his “pathway to get there,” calculated the amount of money it would take to be competitive in early primaries, and even thought about the timing of an announcement. He thinks his family would be on board. “I’m taking a very full look at it,” he says.

And why not. The Republican field is wide open. And Obama is vulnerable. [Emphasis mine]

Not to tout this book too much, but Republicans thought the same thing in 1995, when President Clinton seemed weak and vulnerable after Democrats' historic losses in the 1994 midterm elections. Here's Taylor Branch on how Republicans viewed the party nomination contest in 1995:

His [Clinton's] opponents were multiplying for obvious reasons. Each one saw the GOP nomination as tantamount to election. "They all think they can beat me," he said. "They have weakened me with health care and the midterms, so they'll just finish me off in 1996."

By that point in 1995, Phil Gramm, Lamar Alexander, Richard Lugar, and Pete Wilson (the former governor of California) had announced their presidential campaigns. Obviously, none succeeded, and in retrospect, they weren't the strongest candidates, outward appearances notwithstanding. I don't know enough about John Thune to judge his quality as a presidential nominee, but it's worth noting that similar political circumstances led a host of politicians to greatly underestimate President Clinton's political health. John Thune might be the next president of the United States, but he might also join a long list of men who thought they had it and were sorely disappointed by reality.